Production of conjugated diolefins



Patented Feb. 27, 1945 PRODUCTION OF CONJUGATED DIOLEFINS James L. Amos,Midland, and Frederick J. Soderqulst, Bay City, Mich, aslignors to TheDow Chemical Company, Midland, Mich., a

corporation oi Michigan No Drawing. Application February 28, 1942,Serial No. 432,825

11 Claim.

This invention relates to the production of conjugated dioieflns andmore particularly to the formation of the same by the dehydrogenation ofolefins containing four to five carbon atoms in the molecule.

It is known that certain olefins may be dehydrogenated in gaseous phaseunder the influence of heat and solid catalytic bodies. such as metalcompounds, porous substances, etc., to form conjugated dioleflns.However, in previouslyknown processes for carrying out suchdehydrogenation diiiiculty has been experienced due to low conversion ofthe olefin to diolefln with consequent low percentages of dioleflns inthe effluent gas mixture, to the cracking o! the olefin to formrelatively large amounts of compounds containing a smaller number ofcarbon atoms in the molecule and to the rapid deposition of carbon onthe catalyst body employed, thus rendering the latter inefiective aftera short period of time.

We have found that alkenes having four to five carbon atoms in themolecule and having an unsaturated straight chain of at least fourcarbon atoms may be dehydrogenated readily, and with a high conversionduring a single pass through the reaction zone, to form conjugateddiolefins by pyrolyzing in the presence of water vapor and a hydrogenhalide catalyst. We have further found that when the dehydrogenation iscarried out in this manner, the use of the usual solid catalytic bodies,such as metal compounds, porous substances, etc., is unnecessary and,consequently. the necessity of frequently stopping the operation toclean or regenerate such solid catalyst is avoided. By using a hydrogenhalide catalyst to promote the reaction, carbonization may be greatlyreduced and the amount of cracking to form by-products having fewercarbon atoms in the molecule than the alkene reactant may be reducedbelow that usual when employing only solid catalysts in the reaction. Anadditional advantage resulting from the use 01' a hydrogen halidecatalyst is that a crude diolefin fraction containing an exceptionallyhigh proportion of diolefin may be recovered from the reacted mixture,thus greatly iaciiitating isolation of purified diolefln from thefraction.

The dehydrogenation is carried out in any suitable manner. e. g., bypassing the alkene, water, and hydrogen halide catalyst in vapor phasethrough heated tubes. Although the process is preferably carried out inthe absence of the usual solid catalytic bodies, it should be mentionedthat such bodies may also be employed ii desired. In

some instances the use of such catalytic bodies will even lead toappreciably better yields of diolefin than when the solid catalytic bodyis omitted. Furthermore, the use oi water vapor and hydrogen halide inthe reaction mixture decreases the deposition oi tree carbon on thecatalytic body and increases the length of time over which the lattermay be used without regeneration. However, the advantages gained by theuse of such solid catalytic bodies do not usually justiiy the addedexpense and inconvenience involved.

The alkene, which may comprise i-butene, 2- butene, Z-methyl-l-butene,Z-methyl-Z-butene, 2-methyl-3-butene, l-pentene, or 2-pentene may arisein any of a number of ways, such as by a cracking operation, bydehydrogenation of a parafiln hydrocarbon. or by the elimination oi ahydrogen halide trom a haloparamn. Although the purity of the reactionproduct depends somewhat on the purity of the alkene used, the inventioncontemplates the use of the alkenes, or mixtures thereof, with at leastminor proportions of other hydrocarbons, such as propane, butane,pentane, propene, isobutene, etc.

The hydrogen halide catalyst may be obtained from any convenient source,such as by the action of sulphuric acid on sodium chloride or asby-product hydrogen halide recovered from a halogenation reactionwherein a hydrogen halide is one of the products. Organic compounds suchas monoor polyhalohydrocarbons, halohydrins, halocarboxylic acids, haloesters, etc, which are capable 0! being decomposed during the pyrolysisto form a hydrogen halide may also be used as a means oi introducing thehydrogen halide into the reaction mixture, and are herein included inthe term hydrogen halide catalyst." In similar manner the term "hydrogenbromide catalyst," as used herein, includes hydrogen bromide andcompounds which decompose during the pyrolysis to form hydrogen bromide.Among the halogen compounds which may be incorporated in the reactionmixture and which decompose during the pyrolysis to iurnis'n a hydrogenhalide are ethylene chloride, ethyl bromide, propylene bromide, proplychloride, butyl bromide, butyl chloride, butyl iodide, butylene bromide,butylene chloride, amyl bromide, allyl bromide, ethylene bromohydrin,ethylene chlorchydrin. propylene chlorohydrin, chloroacetic acid,bromoacetic acid, ethyl. chloroacetate. ethyl bromoacetate, chloroethylacetate, etc. The use of haloparaffins having the same number of carbonatoms in the molecule as the diolcfln being produced is particularlyadvantageous, since during the decomposition of the haloparaflin toproduce a hydrogen halide, the desired conjugated diolefln is usuallyalso formed. Mixtures of hydrogen halide catalysts may be used, ifdesired. When hydrogen chloride is used, its constant boiling mixturewith water may be employed advanta' seously, since the use of suchmixture simplifies the introduction of the acid and water in constantproportion into the reaction mixture. Furthermore, the constant boilingmixture may be condensed readily from the reacted mixture, if desired,and natively, the water may be introduced as steam into the reactionmixture.

The proportions of the reactants will, of

course, vary somewhat with the particular alkene be re-used in theprocess. Alterand hydrogen halide catalyst used and also with Llu:reaction conditions which are employed. Thus, under otherwise comparableconditions, hydriodic acid is more eflective than hydrobromic acid,which, in turn, is more eflective than hydrochloric acid. Less than onechemical equivalent, usually from 0.01 to 0.8 chemical equivalent ofhydrogen halide catalyst is used for each moi of alkene. It should bementioned that a chemically equivalent proportion oi hydrogen halidecatalyst is considered herein as being equal to the molecular proportionof the same divided by the number of halogen atoms in the molecule. From1 to 60 'mols, preferably i'roin to 45 mols, oiwater is used for eachmoi of alkenc, although larger proportions of water may be used, ifdesired. It is, of course. obvious that the use of excessive proportionsof water may render the process less economical due to the larger amountof heat required to bring the mixture to the pyrolyzing temperature.

The reactants are usually preheated separately before being mixedtogether and subjected to the pyrolysis, although they may be heatedafter being mixed. if desired. The steam may be. advantageouslysuperheated and mixed with the other ingredients to supply the heat ofpyrolysis to the mixture. It should be mentioned that corrosion of theequipment used for handling the reactants may be greatly reduced byintroducing the hydrogen halide catalyst in the form of a compound whichdecomposes in the reaction zone to liberate a hydrogen halide or, incase a hydrogen halide is used, by admixing it, preferably withoutpreheating, with the other ingredients just prior to the entrance of thereaction mixtime into the reaction zone.

Although the reaction temperature depends somewhat upon the hydrogenhalide catalyst used and the proportion thereof in the reaction mixture,[.18 dehydrogenation is usually carried out at temperatures between 600and 950 C., preferably between 650 and 900 C. The time of pyrolysis isusually measured by the spacevelocity of the alkene within the reactionzone. The space velocity of the alkene may be defined us the number ofcubic feet of gaseous alkene, r ferred to standard conditions of 0 C.,and 760 mm. of mercury pressure, passing through the reaction zone perhour per cubic foot of reaction zone. It should be noted that the spacevelocity rs defined above refers to the alkene in the re action mixtureand not to the reaction mixture as a whole. Thus, the space velocity ofthe aikene may be spoken of independently of the composition of thereaction mixture. The space velocity of the alkone is usually maintainedbetween 200 and 600, and preferably between 250 and 500. Higher or lowerspace velocities may, of course, be maintained if desired. Thedehydrogenation is usually carried out at atmospheric pressure, buthigher or lower pressures may be used.

The use of the dioxides of sulfur and selenium in the pyrolysis mixtureas disclosedin our copending application Serial No. 432,824 increasesthe effectiveness of the hydrogen halide catalyst in promoting theformation of the diolefin. Such oxide is usually used in an amountcorresponding to between 0.01 and 0.6 me] for each mol of alkene. Thesulphur dioxide may be introduced in gaseous phase, and the seleniumdioxide may conveniently be dissolved in the water and the solution thenheated and vaporizedlor atomized into the reaction zone. The sulphur andselenium dioxides are largely converted during thepyrolysis intohydrogen sulphide and hydrogen selenide. respectively.

After the pyrolysis. the reacted mixture=whlch.. comprises water vapor,a hydrogen :halide, lthet,

conjugated diolefln. i. e., 1.3-butadiene or a methylbutadiene, and anyunconverted alkene together, usually, with minor amounts of Battle?rated and unsaturated hydrocarbons having a different number or carbonatoms in the. mole--: cule than the alkene used, may be treated'in any:of a number of ways to recover the conjugated:

diolefln formed during the pyrolysis. For example, the gaseous mixturemay be cooled to I condense out an aqueous solution of the hydrogenhalide which may either be discarded or returned to the pyrolysis stop.The uncondensed portion" may be scrubbed with water to remove any remaining traces of hydrogen halide. and ,the

washed gases then iractionally condensed to recover the unreacted alkeneand the formed -dioleflnas a liquid fraction containing a highwconcentration of the latter. The mixture. oi

alkene and diolefin may then be separated intoits components in knownmanner, e. 3.. by extraction with a selective solvent for the diolefln.or by reaction of the diolefln with a reagent such as cuprous chlorideto form an insoluble complex salt, to recover substantially pure con-Jugated dlolefin and an alkene fraction which, may, if desired, bereturned to the pyrolyzing.

step. In some instances the mixture of alkene and dlolefin may be useddirectly as a source of diolefln, e. g., in the preparation ofsulphones.

of diolefins by selective reaction of the diolefln.

in the hydrocarbon mixture with sulphur dioxide. Hydrogen sulphide orhydrogen selenlde, ii

present in the reacted mixture are partially removed during thescrubbing with water, but are contained principally in the vent gasesafter separation of the fraction containing the alkene and diolefln. Thevent gases may be discarded or, in case they contain the relativelyvaluable" selenium, they may, if desired, be burned to recover thelatter as the dioxide which may be reused in the pyrolysis step.

The accompanying table shows the results of a number of experimentscarried out at atmospheric pressure in each or which one moi oi thealkene listed was passed together with the noted amounts of steam and ofthe indicated hydrogen halide catalyst through a heated reaction chemher. The pyrolysis conditions, i. e., the spacevelocity of the alkeneand the temperature. are A noted for each experiment together with themole oi alkene recovered. the mole of conjugated" di- .i olefin formed,and the male 0! diolefln formed per mol allrene consumed. In the lastcolumn at a temperature in the range 600' to 900 C. and is listed theper cent diolefln in the recovered recovering a conjugated diolefln fromthe re- !raction containing the alkene and dlolefln prior acted mixture.

to separation into its components. 4. The method for preparingLB-butadiene Table Pyrolysis conditions MOI Moi Per cent Ex Moi H dro anM0 M01 can u Mad diolefln dlolelln N Alkene alkene all 0 mm t n m alkenea g formed per in alkenc- 0. used catalyst 75 B one Toma, recoveredarmed moi alkcne dlolefln vc oolty O. consumed Motion 1 1 None 380 7750. 718 0. 081 0.191 7. 1 2 i ROI 0. l 10 87 i 775 0. 572 0. 1M 0. 24816- 8 3--- 1 H51 1. 0 10 370 770 0. 042 0. 147 0. 411 I). 9 4. 1 H31 0.1 10 B72 770 0. 380 0. 228 0. 373 80. 2 5. l KB! 0. l 10 375 825 0. 153(it 83 0. ill. 0 0. 1 H31 0. 01 10 300 775 0. 497 0. 146 0. 288 I1. 0 7.1 HI 0. 1 10 375 775 0. 605 0. 217 0. 00 26. 0 a... 1 Hi i 0.01 10 372775 0. 008 0.100 0.303 21.2 0 l HBr i 0. l 10 350 825 0.155 0. 080 0. 4608.0 10... l H131 0. l 10 B50 0. 28 0.860 0. 54 48.0 11... 1 BI'GBHIOH0.1 10 372 800 0.288 0.320 0.45 60.0 12... l Cal-111B! 0.01 10 3']! (LI!0.23 0.28 63.0 11L. Mixture oi l-hutene 1 1 HC] 0.9 16 7. 5 1 550 775 0.405 0. 2 0. 411 34.0

and zbutene. MU, l 110] 0.92 7.5 350 750 0.52 0.207 0.505 H 31.2 15.Crude butane I 1.0 5.0 034 150 0. 34 0.20 0.30 no 10 .do. 1.0 Hiir 0.170.1 I 348 725 0. i1 0. 20 0.41 28.0 11. do. i 1.0 7.0 370 125 0.37 0.100.24 22.! iii... .110. 1.0 Illir 0.20 8.1 l 340 700 0. 31 0.28 0.45 38.2liL. Crude )entcne 1.0 [Iiir 0.18 7. I 3 305 725 0. 123 0. 37 0. 41 06.8 20..." do. l 1.0 as 200 125 0.54 0.17 can 204 Reaction mixture alsocon tained 0.05 mol sulphur dioxide.

1 Reaction chamber packec with 4-10 mesh pumice.

Reaction chamber packed with 4-8 mesh activated alumina.

' Reaction chamber packed with 4-8 mesh natural bauxite.

5 (proposition 0! crude buteiic: n-butene 81.87, iso-butcne 14.67 butane2.5 combined high and low boiling fractions 1.1%. i Composition 0i crudepentcno: pcutenes 06.9 pentane 2.8%, high boiling raction 1.3%.

Other modes of applying the principle 0! our which consists in passing agaseous mixture cominvention may be employed instead of those exprisinga normal butene, water vapor, an oxide plained, change being made asregardsthe methselected from the class consisting of sulphur diod hereindisclosed. provided the step or steps oxide and selenium dioxide, and ahydrogen halstated by any or the following claims or the ide catalystthrough a reaction zone maintained equivalent of such stated step orsteps be emat a temperature in the range 600 to950 C. ployed, 5. Themethod for preparing 1.3-butadiene We therefore particularly point outand diswhich consists in passing a gaseous mixture comtinctly claim asour invention: prising a normal butene. water vapor, an oxide 1. Themethod for preparing a conjugated diselected from the class consistingof sulphur diolefin which consists in passing a gaseous mixoxide andselenium dioxide, and a hydrogen halture comprising an alkene containingfrom four ide catalyst at a space velocity of 200 to 600 to flve carbonatoms in the molecule and having through a reaction zone maintained at ateman unsaturated straight chain of at least four peraturc in the range600 to 950 0. carbon atoms, water vapor, an oxide selected 0. The methodfor preparing LB-butadiene from the class consisting of sulphur dioxideand which consists in passing a gaseous mixture comselenium dioxide, anda hydrogen halide catalyst prising one molecular proportion of a normalthrough a reaction zone maintained at a tembutene, from 1 to molecularproportions of perature in the range 600 to 950 C. water vapor, from0.01 to 0.6 molecular propor- 2. The method for preparing a conjugatedditions of an oxide selected from the class consistolefin which consistsin passing a gaseous mixing of sulphur dioxide and selenium dioxide andtore comprising an aikene containing from four from 0.01 to 0.8chemically equivalent proportions to five carbon atoms in the moleculeand having 01 a hydrogen halide catalyst at a space velocity anunsaturated straight chain of at least four or from 200 to 600 through areaction zone maincarbon atoms, water vapor, an oxide selected tained ata temperature in the range 600 to from the class consisting of sulphurdioxide and 950' c. selenlm dioxide, and a hydrogen halide catalyst 7.The method for preparing 1.3 blitadiene at a space velocity of from 200to 600 through a which consists in passing a gaseous mixture comreactionzone maintained at a temperature in 00 prising one molecular proportion01' a normal the range 650 to 900 C. and recovering a conbutene, from 3to 45 molecular proportions of jugated diolefln from the reactedmixture. water vapor. from 0.01 to 0.6 molecular propor- 3. The methodfor preparing a conjugated ditions of an oxide selected from the classconsistolenn which consists in passing a gaseous mixing of sulphurdioxide and selenium dioxide and ture comprising one molecularproportion of an from 0.01 to 0.8 chemically equivalent proportionsalkene containing from four to five carbon atoms of a hydrogen bromidecatalyst at a space vein the molecule and having an unsaturated locityof from 250 to 500 through a reaction straight chain 0! at least iourcarbon atoms. zone maintained at a temperature in the range from 3 to 45molecular proportions of water va- 650 to 900 C. and recovering1.3-butadiene por. from 0.01 to 0.6 molecular proportions of from thereacted mixture. an oxide selected from the class consisting of 1110- 8.The method for preparing l.3-buto.di phur dioxide and selenium dioxide,and from 0.01 which consists in passing a gaseous mixture comto 0.8chemically equivalent proportions of a hyprising one molecularprgportlon of a normal drogen halide catalyst at a space velocity offrom butene, from 3 to 45 molecular proportions of 200 to 600 through areaction zone maintained 70 water vapor. from 0.01 to 0.8 molecularpropor- 9. The method for preparing L3butadiene which consists inpassing a gaseous mixture comprising one molecular proportion of anormal butene, from 8 to 45 molecular proportions of water vapor,sulphur dioxide and from 0.0l to 0.8 molecular proportions of hydrogenbromide at a. space velocity oi from 200 to 600 through a. reaction zonemaintained at a temperature in the range 850 to 900 C.

10. The method for preparing LIi-butadiene which consists in passing agaseous mixture comprising one moleculor proportion of a normal butene,from 3 to 45 molecular proportions of water vapor. from 0.01 to 0.6molecular propornormal:

time oi sulphur dioxide and from 0.01 to 08 molecular proportions ofhydrogen brqmldomtp space velocity or from 200 loflflflithrouehmloaction zone maintained at a tempornwreiintlie range650' to 900 C.

11. The method for preparing LS-buisdleiie which consists in passing a.gaseous mixturecomprising one molecular proportion of a. normal butane,from 3 to 45 molecular proportions oi water vapor. from 001 to 0.6molecular proportions or sul hur dioxide and vfrom 0.01 to Olachemically equivalent proportions of a hydrogen chloride catalyst at aspace velocity oi from 200 to 600 through a reaction zone maintained ata. temperature in the range 050' to 000 C. and recovering 1.3-butadienefrom the reacted mixture.

JALIES L. AMOS. FREDERICK J. SODERQUIBT.

